In a National Institutes of Health (US) study, researchers compared the results from reducing total calories consumed by 30% from a baseline balanced diet, first by reducing carbs and keeping fats at baseline, then keeping carbs at baseline and reducing fats by 30%.
The carb-reduced diet was effective in lowering insulin and increasing fat burning leading to weight loss. But “participants lost even more body fat during fat-restricted diet, as it resulted in a greater imbalance between the fat eaten and fat burned”, NIDDK investigator and study author Kevin Hall, Pd.D. said. “These findings counter the theory that body fat loss necessarily requires decreasing insulin, thereby increasing the release of stored fat from fat tissue and increasing the amount of fat burned by the body.”
“But the real world is more complicated than a research lab, and if you have obesity and want to lose weight, it may be more important to consider which type of diet you’ll be most likely to stick to over time.”
The take home message is whatever type of diet you choose, its important to eat low GI carbs. Since lowering insulin is the mechanism of fat loss when reducing carbs, then you can achieve this also by eating lower GI carbs. You don’t want to be doing the opposite by raising your insulin with hi GI carbs which will reduce fat burning.
Nor does this result let sugar off the hook. Carbs are made of complex chains of glucose molecules, but when we talk about sugar we mean it contains fructose as well. Fructose is the ‘sweetener’ and is usually added to foods for this reason. We did not evolve with significant availability of Fructose and its metabolism has a different pathway to glucose and may be problematic today because of its prevalence.
Fructose is also implicated in our behavioural responses to food which can make healthy food choices more difficult.